The adrenal specific toxicant mitotane directly interacts with lipid membranes and alters membrane properties depending on lipid composition

Mitotane (o,p'.-DDD) is an orphan drug approved for the treatment of adrenocortical carcinoma. The mechanisms, which are responsible for this activity of the drug, are not completely understood. It can be hypothesized that an impact of mitotane is mediated by the interaction with cellular membranes. However, an interaction of mitotane with (lipid) membranes has not yet been investigated in detail. Here, we characterized the interaction of mitotane and its main metabolite o,p'-dichlorodiphenyldichloroacetic acid (o,p'-DDA) with lipid membranes by applying a variety of biophysical approaches of nuclear magnetic resonance, electron spin resonance, and fluorescence spectroscopy. We found that mitotane and o,p'-DDA bind to lipid membranes by inserting into the lipid-water interface of the bilayer. Mitotane but not o,p'-DDA directly causes a disturbance of bilayer structure leading to an increased permeability of the membrane for polar molecules. Mitotane induced alterations of the membrane integrity required the presence of phosphatidylethanolamine and/or cholesterol. Collectively, our data for the first time characterize the impact of mitotane on the lipid membrane structure and dynamics, which may contribute to a better understanding of specific mitotane effects and side effects.

Lipoprotein-Free Mitotane Exerts High Cytotoxic Activity in Adrenocortical Carcinoma

CONTEXT

Mitotane (o,p'-DDD), the only approved drug for advanced adrenocortical carcinoma (ACC), is a lipophilic agent that accumulates into circulating lipoprotein fractions and high-lipid-containing tissues.

OBJECTIVE

The aim of our study was to evaluate the in vivo and in vitro biological implication of serum lipoproteins on pharmacological action of mitotane. Distribution and concentration of mitotane were studied in plasma and adrenal tissue samples from mitotane-treated patients. The effect of lipoprotein-bound or lipoprotein-free (LP-F) mitotane was analyzed on proliferation and apoptosis of human adrenocortical H295R cells. A retrospective study of patients with ACC treated or not with statins was also performed.

RESULTS

o,p'-DDD distribution among very low-density lipoprotein, low-density lipoprotein (LDL), high-density lipoprotein (HDL), and LP-F fractions obtained after plasma ultracentrifugation of 23 of mitotane-treated patients was widely distributed in each subfraction. A positive correlation was observed between mitotane levels in plasma and in LDL, HDL, but also LP-F compartment. Intratumor o,p'-DDD concentrations in five ACC samples of mitotane-treated patients were found to be independent of cholesterol transporter expression, scavenger receptors, and LDL receptors. In vitro studies showed significant higher antiproliferative and proapoptotic effects and higher cell and mitochondrial uptake of mitotane when H295R cells were grown in LP-F medium. Finally, retrospective study of an ACC cohort of 26 mitotane-treated patients revealed that statin therapy was significantly associated with a higher rate of tumor control.

CONCLUSIONS

Altogether, our in vitro and in vivo studies provided compelling evidence for a greater efficacy of LP-F mitotane. Patients with ACC may thus benefit from therapeutic strategies that aim to increase LP-F mitotane fraction.

Structural requirements for mitotane activity: development of analogs for treatment of adrenal cancer

AIM

Mitotane is used in adrenal cancer as adjuvant therapy, monotherapy or combined with other cytotoxic agents in advanced disease, but only 30% of patients respond. The aim of this study was to define the structural requirements for drug activity and to develop analogs with improved adrenalytic action.

MATERIALS AND METHODS

Nine analogs of [1-(2-chlorophenyl)-1-(4-chlorophenyl)-2,2dichloroethane] (o,p'-DDD) were tested by measuring suppression of cortisol secretion and the presence of inflammatory changes in the dog adrenal and inhibition of cell proliferation and cortisol production by NCI-H295 human adrenal cancer cells.

RESULTS

In addition to mitotane, o,p'-DDClBr and o,p'-DDBr(2), were active in vitro and in vitro: Their effects were comparable to that of o,p'-DDD when tested at 50 μM concentration, but o,p'DDBr(2) was significantly more active at the lower 20 μM concentration.

CONCLUSION

A dihalogenated methine carbon is required for adrenalytic activity. A change in the aromatic portion of the mitotane molecule causes loss of activity. Because of its greater activity at lower concentrations, o,p'-DDBr(2) has potential application in the treatment of patients with adrenal cancer.

Mitotane treatment for adrenocortical carcinoma: an overview

Adrenocortical carcinoma (ACC) is a rare aggressive endocrine neoplasm characterized by a 5-year survival of less than 50%. Due to the widespread use of imaging techniques in clinics, ACC is increasingly recognized as an incidentally discovered tumor. Mostly characterized by poor prognosis, ACC is often diagnosed at an advanced stage of disease. Early diagnosis is uncommon; when diagnosed, ACCs are usually large and have invaded adjacent organs, even if metastatic spread to distant sites can be absent. Complete surgical resection is the only potentially curative treatment for patients with localized disease; however, due to a recurrence rate of 50-70% after apparent radical surgery, there is a strong rationale for a concomitant systemic treatment. Adrenolytic therapy with mitotane (o,p›-DDD), administered alone or in combination with others antineoplastic agents, is the primary treatment for patients with advanced ACC and is increasingly used also in an adjuvant setting, even if controversy exists on this issue due to the limitations of the available literature. Despite being in use for many years, the rarity of ACC precluded the organization of randomized trials; thus, many areas of uncertainty and controversy remain regarding the role of this old drug in the clinical management of patients with ACC. The purpose of this paper is to review the current evidence on mitotane treatment in patients with advanced disease and in ACC patients after complete surgical resection as adjuvant treatment.

Synthesis of 2-(4-chlorophenyl)-2-(4-chloro-3-thiophenol)-1,1-dichloroethene (3-SH-DDE) via Newman-Kwart rearrangement - a precursor for synthesis of radiolabeled and unlabeled alkylsulfonyl-DDEs

For the first time, a pathway for synthesis of 2-(4-chlorophenyl)-2-(4-chloro-3-thiophenol)-1,1-dichloroethene (3-SH-DDE), is presented. The compound is of particular interest as a precursor for synthesis of alkylsulfonyl-DDE containing different alkyl groups to discover structural activity relationships, and to promote synthesis of radiolabeled methylsulfonyl-DDE. 2-Chloro-5-methylphenol was first methylated and further oxidized to the corresponding benzoic acid. The acid was reduced to the corresponding aldehyde (4-chloro-3-methoxy benzaldehyde) via 4-chloro-3-methoxy-benzene methanol. A lead/aluminium bimetal system was used to carry out the reductive addition of tetrachloromethane to 4-chloro-3-methoxy benzaldehyde to obtain 2,2,2-trichloro-1-(4-chloro-3-methoxyphenyl)ethanol, the desired starting material to synthesize the DDT-analogue (2-(4-chlorophenyl)-2-(4-chloro-3-methoxy-phenyl)-1,1,1-trichloroethane). Elimination of hydrochloric acid and removal of the methyl group led to the 3-OH-DDE. The Newman-Kwart rearrangement was applied to convert 3-OH-DDE to 3-SH-DDE via the dimethylcarbamothioate derivative. 3-SH-DDE is then used as a precursor for the radiolabel synthesis. The overall yield to acquire 3-SH-DDE after 11 steps was 3%. The step with the lowest yield was the DDT-analog synthesis with a yield of 30%. All other step had a yield of >50%. 3-SH-DDE was methylated with (14)C-labeled iodomethane and oxidized by hydrogen peroxide to obtain 3-[(14)C]MeSO(2)-DDE in an overall yield of 30%.

Determination of chiral ratio of o,p-DDT and o,p-DDD pesticides on polysaccharides chiral stationary phases by HPLC under reversed-phase mode

A simple and reliable HPLC method for the chiral resolution of o,p-DDT and o,p-DDD is described. The enantiomeric resolution of o,p-DDT and o,p-DDD has been achieved on Chiralpak AD-R, Chiralcel OD-R, and Chiralcel OJ-R chiral stationary phases. The mobile phases used were acetonitrile-water (50:50 [v/v]) and acetonitrile-2-propanol (50:50 [v/v]) at a flow rate of 1.0 mL/min. For both pesticides detection was done at 220 nm. The values for o,p-DDT of alpha and R(s) varied from 1.24 to 2.52 and from 0.80 to 2.47, respectively. The values of alpha and R(s) for o,p-DDD were 1.26 and 0.60, respectively.